Embodiments herein generally relate to the calibration of optical sensors and more particularly to correcting for foreign matter debris that may be located on the calibration surface.
Often optical sensors are used in environments that suffer from constant debris sources. For example, optical sensors used within media paths can be constantly exposed to media-type debris. Many times optical sensors are calibrated by scanning a calibration surface of a known uniform color. This calibration surface is usually a uniform white surface and, therefore, the calibration surface is sometimes referred to as a “white reference.”
When the white reference calibration surface is contaminated with foreign matter debris, this can undesirably alter the calibration of the portions (pixels) of the sensor that observed for the debris instead of serving the calibration surface. More specifically, the affected pixels will be calibrated as though the color white is the color of the debris and this will affect all future items scanned by the affected pixels until the calibration surface is cleaned and the scanner is recalibrated.
For example, FIG. 1 illustrates an undesirable line 102 within a scanned image 100. This undesirable line 102 is caused by one or more pixels that were improperly calibrated because foreign matter debris was present on the calibration surface during calibration. The items scanned will pass between the scanner and the calibration surface, causing the improperly calibrated pixels to create the undesirable line 102. With conventional systems, the undesirable line 102 will occur in all scanned images until the calibration surface is cleaned and the scanner is recalibrated.